Process of manufacturing an aluminum alloy



Patented May 28, 1935 PATENT OFFICE PROCESS OF MANUFACTURING AN ALUMINUMALLOY Ernest W. Weethofl, Detroit, Mich.

No Drawing.

SOlalms.

jlhe invention relates to-metals and it has particular relation to ametal alloy and a process for manufacturing it.

One object of the invention is to provide a 8 method of producing analuminum chromium allay, which enables combining a substantial amount ofchromium with the aluminum.

Another object of the invention is to provide a method of producing analuminum chromium alloy which enables introduction of the chromiumwithout raising the temperature of the aluminum undesirably above itsmelting point.

Another object of the invention is to provide a method of producing analloy including aluminum, copper and chromium.

Another object of the invention is to provide an improved method ofintroducing one metal into another to produce an alloy.

Another object of the invention is to provide an improved aluminum andchromium alloy.

Other objects of the invention will become apparent from the followingdescription relating to a particular application thereof, and from theclaims hereinafter set forth. g

The introduction of chromium into aluminum alloys is advantageous inthat it increases the strength, hardness, resistance to corrosion andwear, and decreases the coeflicient ofthermal expansion of the alloy.These characteristics are retained at-higher working temperatures andare important advantages particularly in the use of the alloy in pistonsfor internal combustion engines as the piston is subjected to fairlyhigh temperatures, and such'eharacteristics naturally are to be' desiredto increase the life and efficiency of the piston.

As an example of the alloydt may comprise approximately l i i PercentCopper '9' to 12 Chromium 1 to 3 Silicon Magnesium 0.3 Iron 0.8 to 1Remainder-aluminum It has been determined, however, that the processhereinafter to be described enables incorporating a much largerpercentage of chromium into the aluminum, but-the percentage above setforth probably would be satisfactory for most alloys, and particularlyfor pistons for the reasons previously mentioned. The magnesium and ironhave additive value in increasing the hardness of the, alloy, and it isto be understood that while Application September 18, 1933, SerialNassau it is preferred to use magnesium and iron, desirable alloys maybe made without adding these metals.

In preparing the alloy, aluminum is reduced to its molten state byincreasing its temperature to its melting point of 1217" F. andpreferably the temperature will be further increased to approximately1300 F. This temperature, while above the melting point, is notsufficient to appreciably harm the physical properties of the aluminum,whereas if the temperature is further increased the physical propertiesof the aluminum become more appreciably-harmed and this in turn wouldmore appreciably injure the alloy.

While the temperature of 1300 F. is satisfactory, /l5

it may be varied, although it is not desired to increase the temperatureof the aluminum to a point where its structure or physical propertiewould be injured undesirably.

' The chromium and copper are added as fol-' lows. Copper is formed instrips and by well known electrolytic processes, chromium iselectroplated on the copper. The size and thickness of the copper may bevaried according to the proportion of chromium desired, as it isdesirable to have a thin plating of chromium. Thin strips of copper .010to .012 of an inch in thickness have been used with very satisfactoryresults.

' Aft er plating the copper with chromium, with the amount of copper andchromium predetermined, so as to add the proper amount of copper andchromium to the aluminum, the plated strips are introduced into thealuminum, and usually it is better to then agitate the molten mass. Thecopper and chromium become disintegrated. and are absorbed in the moltenaluminum and may uniformly be distributed by the agitati g process.

Silicon is added inthe form of a silicate, such as sodium silicate, andits addition may result in the formation of aluminum oxide, which may 1be skimmed from the top of the molten mass.

The silicon when added in .the form of silicate tends to improve thephysical properties of the alloy by refining its grain structure andmicro structure, as it seems to settle in the grain boundaries of themetaland acts as a binding agent between grains. Silicon so added as asilicate increases the aflinity of chromium for aluminum and is helpfulin the-process of disintegrating or absorbing the chromium.

Instead of first melting the aluminum and then adding the chromium,copper and silicate, the chromium plated copper and silicate may beplaced in the melting pot along with the melted aluminum. 1! magnesiumor iron are to be added, they may be added in any well known andconventional manner.

The resulting alloy is extremely hard and resistant to wear. Moreover,it is extremely strong. These properties render the alloy very suitablein cases where metal is subjected to wearing conditions and strength isrequired. The alloy also has a decreased thermal coeflicient ofexpansion and this is especially desirable where the alloy is subjectedto temperature changes and changes in size and dimensions must bemaintained at a minimum. Particularly, the alloy is very desirable forpistons, as strength, hardness, wear and corrosion resistance and lowercoeflicient of heat expansion are important factors in the life andsatisfactory operation of the piston, and it is important that theseproperties be retained at high working temperatures. This alloy used forpistons, has the advantages of both the well known iron and light metalpistons, while being substantially free of the disadvantages thereof.

Although only one form of the invention has been described, it will beapparent to those skilled in the art that various modifications may bemade without departing from the scope of the appended claims.

I claim:

1. The process of making an aluminum and chromium alloy, which comprisesreducing the aluminum to a molten state, and adding chromi-' um in theform of an electroplated deposit.

2. The process of making an alloy of aluminum, chromium and copper,which comprises reducing the aluminum to a molten state, and adding thechromium and copper in the form of a strip of copper upon which chromiumis electroplated. 3. The process of making an alloy of aluminum,chromium and copper which comprises reducing chromium is electroplatedand maintaining the aluminum in a molten state and at a temperature inproximity to its melting point until the chromium and copper areabsorbed.

4. The process of making an alloy of alumium, chromium and copper, whichcomprises reducing the aluminum to a molten state, adding chromium andcopper in the form of copper electroplated with chromium, and agitatingthe molten mass until the copper and chromium are absorbed.

5. The process of making an alloy of alumium, chromium and copper, whichcomprises reducing the aluminum to a molten state, adding a smallquantity oi silicon in the form or a silicate to the aluminum, andadding chromium and copper in the form of copper electroplated withchromium.

6. The process of making an alloy comprising aluminum and chromium,which includes reducing the aluminum to a molten state andadding thechromium in the form of chromium thinly electroplated upon the exteriorof another metal Plate.

7. The process of making an alloy comprising aluminum, chromium andsilicon which comprises reducing the aluminum to a molten state, addinga small quantity of silicon in the form of silicate and adding chromiumin the form of chromium electroplated on another metal while taining thetemperature of the aluminumat a degree sufiicient to reduce it to amolten state but insumcient to injure its physical properties.

8. The process of making an alloy of aluminum and chromium whichcomprises reducing the aluminum to a molten state and adding chromium inthe form of a thin electroplated deposit to the molten aluminum whilemaintaining the temperature of the latter sufliciently low to preventinjury to its physical properties.

